Bearing alloy



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UNITED; STATE czmrsrorm 1H. or serum,

m 203x, ASSIGNOB r LUIEN mums or nmn q'imw roux.- A conronn'rrou or imw'yonx V- ZGI 1T0 Drawing. Application fled Jamel,

, invention relates more particularlyalloysused for; bearings" I I It is well known, and experience has amply proven, that a single'homogeneous metal is 5 not suited for hearing purposes,and that the first requirement for, a bearing metal is that it be an alloy composed of at least twometals,

' or a metal anda metal0id,:which shall have at,

least a limiteddegree 0i solubility while in the molten state; but that upon; cooling it shall Fpartially separate out into dissimilar crystals and thus form the requisite microstructure, which is necessary in; all bearing alloys. his not only necessary that a bearing metal. shall be composed of chemically dissimilar crystals, but it is all important that "these crystalsshall have'a' marked degree of di-flerence in their physical hardness and 'Wearing qualities.

'20 It is essential that all hearing metals should.

he alloysl aving two or'mor'e phases: that is, *"that'they consistof hardfand relatively soft microscopical particles intimately mixedj The functionofthe hardiparticleslor bearing crystals, is to support'the load and resist the Wear when actual metallic contact exists bea tween the beaiin'g surfaces. The functions 7 of theisofter particles are to ,allow the harder particles to adjust themselves to surfacere- .quirementsof the journals and to wear down. 4 slightly below the surface of the harder, thereby forming slight depressions, on the apparently smooth wearing surface of the bearing", in which depressions minute quan tites of the lubricant- .are held at such times Whenthe bearing surfaces are brought into actualmetallic contact with each other. It 'is this characteristic oficertain alloys to form these slight depressions and thus provide the -40 means for retaining a'residu-al amount of the lubricant, that hearing metals, M

' The Wide range of hardness between the hardest crystal and thesoftest crystal in a bearing metal determines its yalue as such.-

1 However, the hardest crystal should at no time be hard enough so as to prove "distinc tively abrasive to the journal, nor'shouldthe softest crystal be soft. enoughto -cause it to '50 fiovc Within the body of the metal when the An alloy which perhaps most characteristically represents a bearing metal is one composed of copper and tin, containing suflicient tin to produce the tin-copper'eutectoid under ordinary I characterizes them as true or delta crystal. Now, it isa-ivell known fact linmetillurgxfliat this oopper-tin'alloy con taining tin to roduce the eutectoid ry conditions, that. chilling oi; rapidly coo the molten to .the solid increases the-physical strength of-this alloy' and that 1! such chilling, the amount of the eutectoid ormed de- "creased and also that if, under extreme eonditionsythis alloy is chilled sufliciently sudden as no eutectoid i sior ned. 1 i i i In the heated molten 513818 the tin is evenly difl'used in the copper. begins the tin tends to separate from the copper so that [the first solidificationdn the copper is richin alpha crystal. If cooling progresses down, the tin l 'as time to more completelyseparate from the copper, with the result thatslowet cooling produces a softeralpha anda larger amount of the delta crystal, thus efl'ecting )5 characteristics best suited for-a bearing metal. On the other hand, chilling hardens the alpha crystaybyretaining a larger amount of tin in, solidso-lution within the same and, likewise, chilling decreases the aggregate amount of the brittle delta crystal; thus for two rea- I sons, -chilling increases'the strength and physical propertiesof this alloy but decreases its value as abearing metal. 1 f

I The-standard alloy now commonly used I in the worm wheels for-automotive drives and for power reduction gears is comp sedof 89 percent copper and 11 percent tin,-together with a" small quantity of 'the deoxi'dizing agent, such. as phosphorus, manganese or the like; This latter constituent is so small that it need not be given further consideration In general service, in both the United ,States and Europe, these Worm wheelsare cast upon a chillaround. their periphery for the'purpose of producingin' that part of the casting a high tensile strength, since it is this periphery where the-teeth are cut that engages'with the driving worm.

I have'discoveredthataviththe addition of a percentage of nickel to this standard copper tin alloy; when made in the usual .way, that three distinct advantagesobtain: an improvement in the strength and elastic limit of the alloy, a marked increase in the bearing "value of the same and the production of an alloy admirably adapted for casting in a metal mold. 1 The advantage secured by the addition of offlmmme from an lit) ' a relatively small percentageof nickel to this alloy is due to the high fusingpoint' of the same and the fact that the atomic volume of nickel is so nearly equal to that of copperand than double-that of copper and that the nattin and forming an alpha or first solidifying ural grouping of the tin atoms differs from y mum amount of nickel WhlCll can beused to that of copper, it being the'body centered tetragonal lattice structure eFor these reasons, when the three metals are in a molten state, the atoms ofthe one having the highest fusing vtemperature tend to orient themselves first, thuscau'sing the nickel to replace the crystahwhich contains a' much lower percentagepf tin than would 'eXistwit-hout the nickel present, and for the reason that the atomic grouping of nickel and copper areiso nearly identical, a small percentage of nickel in the copper has a less hardening effect upon 'the's'ame than a corresponding amount of tin would have; therefore,'a small percentage of v nickel added to this copper-tin alloy results In .general, the presence of 'nickel causes an increase of the aggregateanieunt ofthe delta,

'a larger amount :of'the' latter tolenterlthe 'i'n' 'the production of a softer alpha crystal and'a larger aggregate amount of the hard delta crystal.

Nickeladded 'to' this =alloy in varying amounts has a very distinctand pronounced e'ifectfonthe formation of the delta crystal.

.it replacing the tin in the alpha crystal leaves delta formation, at the same time causes it to form in a--smalle'r or more-finely subdivided state', a condition beneficial to a hearing metaL- When makingthe-all0y with percent of nickel a distinct effect is' reduced upon the eutectoid formation of-the. elta, and increasing from 5 to. l gpercent the delta formation. becomes more andmore striated andqlainellar; and at'ly percent the delta becomes solider massive,-- assuming a coniplete noneutectoid form. This c'onditionob tains for all percentages-of nickel above 1% per cent. The addition of nickel in'all proportions thus producesan effect upon the.

delta crystal so as'to increase, its wear or abrasion resisting capacity. p

advantage when used for castings made in metalor chill molds; inthat it does not have the disadvantage or drawback which the standard 'alloy has. When pouring the standard alloy against a chill, the alpha crystal is hardened by'the fact that a larger percent of tin is held in solid solution in thiscrystal,

v and at the same time a much smaller amount of deltacrystal is formed; The improvedalloy does not posssthese disadvantages for the reason that in the presence of the nickel the'alpha crystal is not hardened by chilling,

amount of t chilled surface The'improv'ed alloy thus and at the same time 'the delta crystal is not i it decreased in like amount, for which reasons the actual chilled surface of the improved alloy. has a soft alpha crystal and a large;

he delta formationsupon the retains its full bearing value even though it is chilled, by retaining a .wide range ofhardness between the hardest and softest crystals. 1

Ithas been found in practice,that the mini advantage-in this standard alloy is one-half of'one percent, and that the largest amount of nickel that'canbeused to advantage is ten percent; when,thow ever, sucha large amount of nickel is used,- it is permissible to cut down the percentage of tin to, say five percent, and still retain the beneficial effects upon the delta crystal, copper being the remain1ngcon-- plish a certain transformation" must be varied.

- In practice varying amounts of lead are often added to'the standard alloy, the'lead having theeife'ct of makingthe metal more plastic, a condition very desirable where con formabilityis necessary. The lead air all practical purposes is present in the form of.

amechanical'miziture and accordingly it may be added'to this improved alloy in manner as heretofore with corresponding. beneficial My invention is such' that-it can be readily practiced by any experienced foundryman versed'in the art. :The'ni'ckel is secured-in the form of a copper-nickel alloy as'commonly found onthe market. The copper,. together with the necessary percent ofal loyednickel is first melted, the deo'xidized agent is then added, and finally the tin, afterwhi ch lead may or may not be added as desiredQ. ,-M y preferred composition is copper 84,5 percent, tin 10.5, nickel 5'perce'nt'.

It is to be understood that the word hearing .as used. in-this application and in the v appended claim is intended to include gear wheels, worm wheels and similar articles which require characterlstics of hardness'and wear resistance, as indicated hereinbefore.

; I'claini as my invention: This improved alloy has avvery distinct in the absence of zinc against a chill so that the-alpha crystal is not hardened but left soft and a large amountof hard delta crystal is formed upon the chilled surfaces-and a wide range offhardness being presentbetween the hardest delta crystal andthe soft-- est alpha crystal,

In testimony whereofl t rab tes signature.

cI-IRIsfrorHER n Bragg; 

